Tin(IV) oxide

Tin(IV) oxide, also known as stannic oxide, is the inorganic compound with the formula SnO2. The mineral form of SnO2 is called cassiterite, and this is the main ore of tin.[9] With many other names, this oxide of tin is an important material in tin chemistry. It is a colourless, diamagnetic, amphoteric solid.

Tin(IV) oxide
3D model of tin (IV) oxide, red atom is oxide
Sample of tin (IV) oxide
Names
IUPAC name
Tin (IV) Oxide
Other names
Stannic oxide, Tin(IV) oxide, Flowers of tin,[1] Cassiterite
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.038.311
EC Number
  • 242-159-0
RTECS number
  • XQ4000000
UNII
  • InChI=1S/2O.Sn ☒N
    Key: XOLBLPGZBRYERU-UHFFFAOYSA-N ☒N
  • (O=Sn=O): O=[Sn]=O
Properties
O2Sn
Molar mass 150.708 g·mol−1
Appearance Yellowish or light grey powder[2]
Odor Odorless
Density 6.95 g/cm3 (20 °C)[3]
6.85 g/cm3 (24 °C)[4]
Melting point 1,630 °C (2,970 °F; 1,900 K)[3][4]
Boiling point 1,800–1,900 °C (3,270–3,450 °F; 2,070–2,170 K)
Sublimes[3]
Insoluble[4]
Solubility Soluble in hot concentrated alkalis,[4] concentrated acids
Insoluble in alcohol[3]
−4.1·10−5 cm3/mol[4]
2.006[5]
Structure
Rutile tetragonal, tP6[6]
P42/mnm, No. 136[6]
4/m 2/m 2/m[6]
a = 4.737 Å, c = 3.185 Å[6]
α = 90°, β = 90°, γ = 90°
Octahedral (Sn4+)
Trigonal planar (O2−)
Thermochemistry
52.6 J/mol·K[4]
49.04 J/mol·K[4][7]
−577.63 kJ/mol[4][7]
−515.8 kJ/mol[4]
Hazards
NFPA 704 (fire diamond)
[8]
NFPA 704 four-colored diamond
1
0
0
Lethal dose or concentration (LD, LC):
> 20 g/kg (rats, oral)[8]
NIOSH (US health exposure limits):
PEL (Permissible)
 none[2]
REL (Recommended)
 TWA 2 mg/m3[2]
IDLH (Immediate danger)
 N.D.[2]
Safety data sheet (SDS) ICSC 0954
Related compounds
Related tin oxides
 Tin(II) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure
Tin (IV) oxide fibers (optical microscope)

Tin(IV) oxide crystallises with the rutile structure. As such the tin atoms are six coordinate and the oxygen atoms three coordinate.[9] SnO2 is usually regarded as an oxygen-deficient n-type semiconductor.[10]

Hydrous forms of SnO2 have been described as stannic acid. Such materials appear to be hydrated particles of SnO2 where the composition reflects the particle size.[11]

Preparation

Tin(IV) oxide occurs naturally. Synthetic tin(IV) oxide is produced by burning tin metal in air.[11] Annual production is in the range of 10 kilotons.[11] SnO2 is reduced industrially to the metal with carbon in a reverberatory furnace at 1200–1300 °C.[12]

Amphoterism

Although SnO2 is insoluble in water, it is amphoteric, dissolving in base and acid.[13] "Stannic acid" refers to hydrated tin (IV) oxide, SnO2, which is also called "stannic oxide."

Tin oxides dissolve in acids. Halogen acids attack SnO2 to give hexahalostannates,[14] such as [SnI6]2−. One report describes reacting a sample in refluxing HI for many hours.[15]

SnO2 + 6 HI → H2SnI6 + 2 H2O

Similarly, SnO2 dissolves in sulfuric acid to give the sulfate:[11]

SnO2 + 2 H2SO4 → Sn(SO4)2 + 2 H2O

SnO2 dissolves in strong bases to give "stannates," with the nominal formula Na2SnO3.[11] Dissolving the solidified SnO2/NaOH melt in water gives Na2[Sn(OH)6], "preparing salt," which is used in the dye industry.[11]

Uses

In conjunction with vanadium oxide, it is used as a catalyst for the oxidation of aromatic compounds in the synthesis of carboxylic acids and acid anhydrides.[9]

Ceramic glazes

Tin(IV) oxide has long been used as an opacifier and as a white colorant in ceramic glazes.’The Glazer’s Book’ – 2nd edition. A.B.Searle.The Technical Press Limited. London. 1935. This has probably led to the discovery of the pigment lead-tin-yellow, which was produced using tin(IV) oxide as a compound.[16] The use of tin(IV) oxide has been particularly common in glazes for earthenware, sanitaryware and wall tiles; see the articles tin-glazing and Tin-glazed pottery. Tin oxide remains in suspension in vitreous matrix of the fired glazes, and, with its high refractive index being sufficiently different from the matrix, light is scattered, and hence increases the opacity of the glaze. The degree of dissolution increases with the firing temperature, and hence the extent of opacity diminishes.[17] Although dependent on the other constituents the solubility of tin oxide in glaze melts is generally low. Its solubility is increased by Na2O, K2O and B2O3, and reduced by CaO, BaO, ZnO, Al2O3, and to a limited extent PbO.[18]

SnO2 has been used as pigment in the manufacture of glasses, enamels and ceramic glazes. Pure SnO2 gives a milky white colour; other colours are achieved when mixed with other metallic oxides e.g. V2O5 yellow; Cr2O3 pink; and Sb2O5 grey blue.[11]

Dyes

This oxide of tin has been utilized as a mordant in the dyeing process since ancient Egypt.[19] A German by the name of Kuster first introduced its use to London in 1533 and by means of it alone, the color scarlet was produced there.[20]

Polishing

Tin(IV) oxide can be used as a polishing powder,[11] sometimes in mixtures also with lead oxide, for polishing glass, jewelry, marble and silver.[1] Tin(IV) oxide for this use is sometimes called as "putty powder"[13] or "jeweler's putty".[1]

Glass coatings

SnO2 coatings can be applied using chemical vapor deposition, vapour deposition techniques that employ SnCl4[9] or organotin trihalides[21] e.g. butyltin trichloride as the volatile agent. This technique is used to coat glass bottles with a thin (<0.1 μm) layer of SnO2, which helps to adhere a subsequent, protective polymer coating such as polyethylene to the glass.[9]

Thicker layers doped with Sb or F ions are electrically conducting and used in electroluminescent devices and photovoltaics.[9]

Gas sensing

SnO2 is used in sensors of combustible gases including carbon monoxide detectors. In these the sensor area is heated to a constant temperature (few hundred °C) and in the presence of a combustible gas the electrical resistivity drops.[22] Room temperature gas sensors are also being developed using reduced graphene oxide-SnO2 composites(e.g. for ethanol detection).[23]

Doping with various compounds has been investigated (e.g. with CuO[24]). Doping with cobalt and manganese, gives a material that can be used in e.g. high voltage varistors.[25] Tin(IV) oxide can be doped with the oxides of iron or manganese.[26]

References
  1. "Material Name: stannic oxide". Museum of Fine Arts, Boston. 2007-02-10. Archived from the original on 2012-11-04. Retrieved 2013-03-29.
  2. NIOSH Pocket Guide to Chemical Hazards. "#0616". National Institute for Occupational Safety and Health (NIOSH).
  3. CID 29011 from PubChem
  4. Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0.
  5. Pradyot, Patnaik (2003). Handbook of Inorganic Chemicals. The McGraw-Hill Companies, Inc. p. 940. ISBN 0-07-049439-8.
  6. Baur, W.H. (1956). "Über die Verfeinerung der Kristallstrukturbestimmung einiger Vertreter des Rutiltyps: TiO2, SnO2, GeO2 und MgF2". Acta Crystallographica. 9 (6): 515–520. doi:10.1107/S0365110X56001388.
  7. Stannic oxide in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 2014-07-04)
  8. "MSDS of Tin(IV) oxide". fishersci.ca. Fisher Scientific. Retrieved 2014-07-04.
  9. Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 447–48. ISBN 978-0-08-022057-4.
  10. Solid State Chemistry: An Introduction Lesley Smart, Elaine A. Moore (2005) CRC Press ISBN 0-7487-7516-1
  11. Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5
  12. Tin: Inorganic chemistry,J L Wardell, Encyclopedia of Inorganic Chemistry ed R. Bruce King, John Wiley & Son Ltd., (1995) ISBN 0-471-93620-0
  13. Inorganic & Theoretical chemistry, F. Sherwood Taylor, Heineman, 6th Edition (1942)
  14. Donaldson & Grimes in Chemistry of tin ed. P.G. Harrison Blackie (1989)
  15. Earle R. Caley (1932). "The Action Of Hydriodic Acid On Stannic Oxide". J. Am. Chem. Soc. 54 (8): 3240–3243. doi:10.1021/ja01347a028.
  16. Hermann Kühn, 1967, "Blei-Zinn-Gelb und seine Verwendung in der Malerei", Farbe und Lack 73: 938-949
  17. ’A Treatise On Ceramic Industries.’ E.Bourry. Fourth edition. Scott, Greenwood & son. London. 1926.
  18. ’Ceramic Glazes’ Third edition. C.W.Parmelee & C.G.Harman. Cahners Books, Boston, Massachusetts. 1973.
  19. Sir Thomas Edward Thorpe History of Chemistry (1909) Vol. 1, pp. 11-12.
  20. Thomas Mortimer, A General Dictionary of Commerce, Trade, and Manufactures (1810) "Dying or Dyeing"
  21. US 4130673, Larkin, William A., "Process of applying tin oxide on glass using butyltin trichloride", published 1978-12-19, assigned to M & T Chemicals Inc.
  22. Joseph Watson The stannic oxide semiconductor gas sensor in The Electrical engineering Handbook 3d Edition; Sensors Nanoscience Biomedical Engineering and Instruments ed R.C Dorf CRC Press Taylor and Francis ISBN 0-8493-7346-8
  23. Jayaweera, M.T.V.P., De Silva, R.C.L., Kottegoda, I.R.M. and Rosa, S.R.D., 2015. Synthesis, characterization and ethanol vapor sensing performance of SnO2/Graphene composite film. Sri Lankan Journal of Physics, 15, pp.1–10. DOI: http://doi.org/10.4038/sljp.v15i0.6345
  24. Wang, Chun-Ming; Wang, Jin-Feng; Su, Wen-Bin (2006). "Microstructural Morphology and Electrical Properties of Copper- and Niobium-Doped Tin (IV) oxide Polycrystalline Varistors". Journal of the American Ceramic Society. 89 (8): 2502–2508. doi:10.1111/j.1551-2916.2006.01076.x.
  25. Dibb A.; Cilense M; Bueno P.R; Maniette Y.; Varela J.A.; Longo E. (2006). "Evaluation of Rare Earth Oxides doping SnO2.(Co0.25,Mn0.75)O-based Varistor System". Materials Research. 9 (3): 339–343. doi:10.1590/S1516-14392006000300015.
  26. A. Punnoose; J. Hays; A. Thurber; M. H. Engelhard; R. K. Kukkadapu; C. Wang; V. Shutthanandan & S. Thevuthasan (2005). "Development of high-temperature ferromagnetism in SnO2 and paramagnetism in SnO by Fe doping". Phys. Rev. B. 72 (8): 054402. Bibcode:2005PhRvB..72e4402P. doi:10.1103/PhysRevB.72.054402.

Further reading
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